Known in the art are systems for adapting a conventional telephone line to a data and voice transmission local network.
In these systems used in local networks the signals are transmitted through the telephone line by means of transmission devices powered from wiring and a power supply source of their own, galvanically separate from the telephone network.
An infrastructure for electrical power supply is therefore necessary, which doubles the installation and maintenance cost.
For example, if it is wished to connect an appliance alarm system using the telephone network, wiring must at present be installed to bring the electrical current to the data transmitter device which will provide the alarm signal from the appliance to be controlled.